Seven less than a number is twenty (as an equation)

You're expression is correct if it's asking for a number that is less than 7. But if the problem is asking for some number less than seven as in seven less some number, then it's 7-n. For example: 4 less than 7 is 7-4.

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step-by-step explanation:

one of the most important purposes of surface treatment is to alter surface properties according to the requirement of specific applications. for example, hydrophobic coating has been utilized on windshield and eyeglasses. gold atom monolayer on substrate has become a popular surface bioconjugation strategy.  

a) 0

step-by-step explanation:

i^413 x i^0 = 0 as any number multiplied by a zero is

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